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AGRC1021 End Sem > Plant and soil nutrition > Flashcards

Plant and soil nutrition Flashcards

(67 cards)

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1
Q

Which layer of soil contains a wide range of organisms?

A

Upper

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2
Q

From which soil layer do plants obtain most of their water and minerals from?

A

The upper layers

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3
Q

How long can soil take to form?

A

Centuries

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4
Q

What are the 3 soil horizons?

A

A, B and C

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5
Q

What is soil horizon A composed of?

A

Topsoil
- Broken down rock, living organisms, decaying organic matter

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6
Q

What is soil horizon B composed of?

A

Less organic matter than A, less weathered

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7
Q

What is soil horizon C composed of?

A

Partially broken down rock

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8
Q

What does the partially broken down rock in horizon C serve as?

A

“Parent” material for minerals that later form the upper horizons

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9
Q

What 3 particles is soil made up of?

A

Sand, silt and clay

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10
Q

What are loams?

A

Soils which comprise approximately equal amounts of sand, silt and clay

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11
Q

What are the organic components of soil?

A

Humus, bacteria, fungi, algae and other protists, insects, earthworms, nematodes, plant roots

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12
Q

What is the role of humus in soil?

A

Prevents clay particles from packing together
- Retains water but is still porous enough to aerate roots

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13
Q

What is soil CEC?

A

Cation exchange capacity

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14
Q

What are the Inorganic components of soil?

A
  • Nitrate (NO3), phosphate (PO4) and sulphate (SO42-)
  • Cations (K+, Ca2+, Mg2+)
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15
Q

What charge do most soil particles have?

A

Negative

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16
Q

What does the charge of soil particles determine?

A

Their ability to bind many nutrients

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17
Q

What is the role of H+ ions in soil?

A

Neutralise the negative charge of soil particles, causing the release of mineral cations

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18
Q

What is soil classified based on?

A
  1. Soil horizons
  2. Distinctive features
  3. Constituent materials
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19
Q

What are the characteristics of vertosol soils?

A
  • Parent materials are commonly volcanic rocks (basalt), clay-rich sediments, and sedimentary rocks
  • Clays are abundant
  • Shrink when dry and swell when wet
  • When dry, cracking can be pronounced and extend to depth
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20
Q

What can soil fertilisation do?

A

Make soil a renewable resource, enabling repeated cultivation at a fixed location

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21
Q

What is soil fertilisation?

A

The addition of mineral nutrients to soil

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22
Q

What has been a recurrent problem
throughout human history with soil?

A

Soil mismanagement

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23
Q

What do wind and water erosion do to soil?

A

Remove large amounts of topsoil

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24
Q

What does soil erosion cause?

A

Soil degradation because nutrients are carried away by wind and streams

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25
What do farmers do to limit soil erosion? (3)
Plant rows of trees as windbreaks, terrace hillside crops, and cultivate crops in a contour pattern
26
What is "no-till" agriculture?
Where a special plough creates narrow furrows for seeds and fertilisers
27
What are some issues with irrigation?
- Huge drain on water resources when used for farming in arid regions - 75% of global freshwater use is devoted to agriculture - Many rivers have been reduced to trickles
28
What does salinity refer to?
The soluble salt content of soil and water
29
How does Australia’s low-lying topography affect salinity?
it ensures that salt enriched pools can form on the soil surface
30
How does "fertilisation" occur in natural environments?
Mineral nutrients are recycled by excretion of animal wastes and decomposition of humus
31
Why is fertilisation needed in agriculture?
- Minerals are extracted from soil and distributed in the food supply chain - As we excrete wastes, these minerals are not returned to the source soil
32
What do fertilisers usually contain?
Nitrogen (N), phosphorus (P) and potassium (K)
33
What does the three-number code on fertilisers represent?
The N—P—K ratio
34
What are some organic fertilisers?
Manure, fishmeal and compost
35
What are the benefits to using organic fertilisers?
- Organic material must be decomposed into inorganic nutrients that roots can absorb - Organic fertilisers can release nutrients more gradually
36
What are the issues with non organic fertiliser?
- Nutrients from chemical fertilisers may not be retained by the soil for long - Excess nutrients are often leached from the soil and can cause algal blooms in lakes
37
What is soil leaching?
Where water percolates through the soil, carrying dissolved nutrients, salts, and other substances
38
How many essential elements are there for plant growth?
17
39
Why are some elements needed for plant growth called macronutrients?
Plants require them in relatively large amounts
40
What are the macronutrients needed by plants?
Carbon, oxygen, hydrogen, nitrogen, phosphorus, sulphur, potassium, calcium, and magnesium
41
Why are some elements needed for plant growth called micronutrients?
Because plants need them in very small amounts
42
What are the micronutrients needed by plants?
Chlorine, iron, manganese, boron, zinc, copper, nickel, and molybdenum
43
What are some common symptoms of plant mineral deficiency?
- Purple colouring - Yellow/brown strip down centre of leaves - Brown wilting at tip
44
What are the most common plant deficiencies?
Nitrogen, phosphorus and potassium
45
How does soil pH influence mineral availability?
It affects soil cation exchange capacity and the chemical form of minerals
46
What are some detrimental effects of soil pH to mineral availability? (2)
1. Minerals may bind too tightly to clay particles 2. Minerals may be in a chemical form that plants cannot absorb
47
What pH do most plants prefer?
Slightly acidic
48
Why do most plants prefer a slightly acidic soil pH?
Because the high H+ concentrations can displace cations from soil particles
49
What type of relationship do plants and soil microbes have?
Mutualistic
50
How do dead plants benefit soil dwelling microorganisms?
Dead plants provide energy needed
51
What is a Rhizosphere?
The layer of soil bound to the plant’s roots
52
What do Rhizospheres contain?
Bacteria that act as decomposers and nitrogen-fixers
53
What do nitrogen fixing bacteria do?
Convert atmospheric nitrogen to ammonia (NH3) and form nodules
54
What does crop rotation take advantage of?
The agricultural benefits of symbiotic nitrogen fixation
55
Which process takes advantage of he agricultural benefits of symbiotic nitrogen fixation
Crop rotation
56
Why are legumes planted?
To restore the concentration of nitrogen in the soil
57
What are Mycorrhizae?
Mutualistic associations of fungi and plant roots
58
How do fungi benefit from mycorrhizae?
A steady supply of sugar from the host plant
59
How does the host plant benefit from mycorrhizae?
- Fungus increases the surface area for water uptake and mineral absorption - Mycorrhizal fungi also secrete growth factors that stimulate root growth and branching
60
What are the 2 main types of mycorrhizal associations?
1. Ectomycorrhizae 2. Arbuscular mycorrhizae
61
What occurs in ectomycorrhizae?
- The fungal mycelium forms a dense sheath over the surface of the root - These hyphae form a network in the apoplast, but do not penetrate root cells
62
What occurs in arbuscular mycorrhizae?
- Microscopic fungal hyphae extend into the root - These mycorrhizae penetrate the cell wall, but not the plasma membrane to form branched arbuscules within root cells
63
Nitrifying bacteria convert ____ to nitrate (NO3-)
Ammonium (NH4+)
64
What are three unusual nutritional adaptations of plants?
1. Epiphytes 2. Parasitic plants 3. Carnivorous plants
65
What is an epiphyte?
A plant that grows on another plant and obtains water and minerals from rain and falling debris
66
What are parasitic plants?
Plants that absorb water, minerals and sometimes products of photosynthesis from their living host
67
What are Carnivorous plants?
Plants that supplement their diet by capturing insects and other small animals

AGRC1021 End Sem (11 decks)

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